I shared few weeks ago the story of how my hens were feeding on their own eggs in a cannibalism that was denying me profits.

Then, I de-beaked the birds and thought I had cured the menace, but it recurred, albeit on another batch of hens.

Last week, my egg production dropped from an average of 77 to about 50 per day from 116 birds due to egg eating.

There are several causes of this strange phenomenon, from overcrowding in the coop, which leads to stress, and nutritional deficiencies particularly lack of Vitamin D and calcium.

When the problem first emerged, I substituted the bone meal in the home-made feeds with commercially prepared Di-Calcium Phosphate (DCP), but this didn’t work until I de-beaked the hens.

This time round, I went ahead to substitute the bone meal with limestone, but again, this also didn’t work. I then decided to double the amount of DCP and limestone in the feed mixture, but the problem persisted. I even de-beaked the birds but there was no change.

I tried an idea my wife had suggested, which involved beating an egg into a creamy liquid, adding ground pepper and, thereafter, offering the birds, but this didn’t work either. Some researchers at University of Florida, US, have found that the bad taste the hens will encounter cures the habit. Perhaps the pepper wasn’t hot enough for my hens.

Desperate, I decided to give bone meal and limestone ad lib first thing every morning before offering any feeds. This way, the birds ingest more calcium in the system.

About 1kg is enough for 100 birds. Initially, during feed formulation, I would add about 500g of limestone or bone meal per 70kg bag but I realised even after doubling this quantity in the process of formulation, the problem persisted, the reason I changed tact.

Other signs of lack of calcium are weak egg shells and eggs break easily when you handle. Also weak bones and difficulty in walking. After four days, my manager, Cleopas called me with some good news. The egg production had shot up to an average of 80 per day.

That means you have to add some limestone and bone meal to supply at least 4g of calcium per day to meet the requirements for eggshell formation.

Ideally, calcium requirements should be specified in terms of amount per day rather than percentage in diet. This is because when it’s very hot, birds consume less calcium.

Of the four natural sources of calcium, that is, oyster shells (38 per cent) contain the highest amount of calcium, followed by limestone flour (37 per cent), Di-Calcium Phosphate (22 per cent) and bone meal (22 per cent).

The best way to determine how much calcium is in your ingredient or feed is to take a sample for chemical analysis. Mr Kuria of Kenya Agricultural and Livestock Research Organisation, Naivasha told me they do not offer the service but you can get it in any other credible laboratory.

It is important to achieve the correct balance between calcium and phosphorus because oversupply of one component interferes with utilisation of the other leading to calcium deficiency and results in weak egg shells and bones.

One must adhere to the calcium to phosphorus ratio. For growing birds, this ratio should be one to one or two to one. For layers, the calcium to phosphorus ration should be six to one.

For calcium and phosphorus to work, they require vitamin D, which can be obtained either from premix or absorbed by the birds from direct sunlight. I buy the ingredients from agrovets and some local feed manufacturers, who are trusted sources.

When I test the natural sources of calcium, I will share the results because I suspect the levels of calcium in the feed ingredients of ready-made commercial feeds may be inadequate.

So, is there anything a farmer can do from the onset as birds grow to curb calcium deficiency? The answer is no because calcium is needed daily by the birds and the requirements double when a hen starts laying eggs. This means, birds must get the right amount of calcium daily, about 4g and there are no reserves in the body.

That is why when the levels drop, they start eating eggs to get the calcium and when you supplement, they get enough and stop. This phenomenon is like a condition called pica affecting pregnant women who start eating stones to supplement the iron deficiency occasioned by increased intake from the growing foetus.

Obwogo is a poultry farmer, a medical doctor and a senior quality improvement adviser in health policy.